Witch Nails (Krt90whnl): A spontaneous mouse mutation affecting nail growth and development.

Numerous single gene mutations identified in humans and mice result in nail deformities with many similarities between the species. A spontaneous, autosomal, recessive mutation called witch nails (whnl) is described here where the distal nail matrix and nail bed undergo degenerative changes resulting in formation of an abnormal nail plate causing mice to develop long, curved nails. This mutation arose spontaneously in a colony of MRL/MpJ-Faslpr/J at The Jackson Laboratory. Homozygous mutant mice are recognizable by 8 weeks of age by their long, curved nails. The whnl mutation, mapped on Chromosome 15, is due to a 7-bp insertion identified in the 3' region of exon 9 in the Krt90 gene (formerly Riken cDNA 4732456N10Rik), and is predicted to result in a frameshift that changes serine 476 to arginine and subsequently introduces 36 novel amino acids into the protein before a premature stop codon (p. Ser476ArgfsTer36). By immunohistochemistry the normal KRT90 protein is expressed in the nail matrix and nail bed in control mice where lesions are located in mutant mice. Immunoreactivity toward equine KRT124, the ortholog of mouse KRT90, is restricted to the hoof lamellae (equine hoof wall and lamellae are homologous to the mouse nail plate and nail bed) and the mouse nail bed. Equine laminitis lesions are similar to those observed in this mutant mouse suggesting that the latter may be a useful model for hoof and nail diseases. This first spontaneous mouse mutation affecting the novel Krt90 gene provides new insight into the normal regulation of the molecular pathways of nail development.

Administrator blindness affects the recording of eyewitness lineup outcomes.

OBJECTIVE: We investigated the effects of administrator knowledge of suspect identity in a lineup (blind vs. nonblind), witness identification (suspect vs. filler), and witness confidence (high vs. low) on whether administrators recorded the identification as an affirmative response; whether administrators recorded qualitative notes regarding the lineup task; and the content of those qualitative notes. HYPOTHESES: We predicted that nonblind administrators would record more identifications of the suspect than the filler, but blind administrators would record such identifications at comparable rates. We predicted this difference would be larger in the low (vs. high) confidence condition. We examined effects on administrators' qualitative notes in an exploratory fashion. METHOD: Undergraduate participant administrators (N = 488) presented a lineup to a confederate witness (who made a scripted identification decision) and completed a record of the lineup task. RESULTS: Nonblind administrators recorded 25% fewer identifications of fillers (vs. suspects), and evaluated witnesses less favorably in the filler (vs. suspect) identification condition (ηp² = .194). Blind administrators were not influenced by witness selection. Blind (vs. nonblind) administrators recorded more qualitative notes, confidence statements, and information relevant to witnesses' decision processes, regardless of whether witnesses identified the suspect or the filler. Among those who recorded a confidence statement, nonblind administrators' characterizations were biased such that independent coders judged witnesses to be more confident in their identifications of the suspect (vs. filler). CONCLUSION: Blind administration eliminates numerous biases associated with administrator expectations and may yield more informative lineup records. These results further support blind lineup reform recommendations. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

A missense mutation in Grm6 reduces but does not eliminate mGluR6 expression or rod depolarizing bipolar cell function.

GRM6 encodes the metabotropic glutamate receptor 6 (mGluR6) used by retinal depolarizing bipolar cells (DBCs). Mutations in GRM6 lead to DBC dysfunction and underlie the human condition autosomal recessive complete congenital stationary night blindness. Mouse mutants for Grm6 are important models for this condition. Here we report a new Grm6 mutant, identified in an electroretinogram (ERG) screen of mice maintained at The Jackson Laboratory. The Grm6nob8 mouse has a reduced-amplitude b-wave component of the ERG, which reflects light-evoked DBC activity. Sequencing identified a missense mutation that converts a highly conserved methionine within the ligand binding domain to leucine (p.Met66Leu). Consistent with prior studies of Grm6 mutant mice, the laminar size and structure in the Grm6nob8 retina were comparable to control. The Grm6nob8 phenotype is distinguished from other Grm6 mutants that carry a null allele by a reduced but not absent ERG b-wave, decreased but present expression of mGluR6 at DBC dendritic tips, and mislocalization of mGluR6 to DBC somas. Consistent with a reduced but not absent b-wave, there were a subset of retinal ganglion cells whose responses to light onset have times to peak within the range of those in control retinas. These data indicate that the p.Met66Leu mutant mGluR6 is trafficked less than control. However, the mGluR6 that is localized to the DBC dendritic tips is able to initiate DBC signal transduction. The Grm6nob8 mouse extends the Grm6 allelic series and will be useful for elucidating the role of mGluR6 in DBC signal transduction and in human disease.NEW & NOTEWORTHY This article describes a mouse model of the human disease complete congenital stationary night blindness in which the mutation reduces but does not eliminate GRM6 expression and bipolar cell function, a distinct phenotype from that seen in other Grm6 mouse models.